Check if that FSB jumper change also changed the memory speed setting.

What memory type are you using?

DDR should be 266Mhz or higher with a 133 MhZ FSB.
SDRAM should be 133 Mhz memory not 100 Mhz.

If you haven't changed the BIOS it should have the timing set for CL2.5 which is fine for any memory. If you set the memory to high performance it could have set CL 2.0 which requires better grade memory to be stable. Check the memory timings.

no offense either, but isn't that what he's doing THIS time (learning more about hardware)? Hey, you gotta start somewhere.

Anyway good luck with the k7vt2. A good basic cheap board to learn the ropes on!!! I had some troubles trying to push the memory too far, so definitely set the mem settings back to cas 2.5 and see if that helps. If I remember there's a bios setting to reset everything back to basic default that you might want to try if you've been mucking about and don't remember exactly what you played with.